Bogie Undercarriage Design With Rigidly Mounted Track Roller

ABSTRACT

An undercarriage is disclosed that may include a rigidly mounted roller near or adjacent to a rear drive sprocket. The remaining rollers and bogies may be flexibly suspended.

FIELD OF THE INVENTION

This disclosure relates to track rollers for undercarriage bogies and, more particularly, to rigidly mounted track rollers.

BACKGROUND OF THE INVENTION

It is conventional to provide undercarriage track rollers and bogies with suspension elements to absorb shock and improve weight distribution as exemplified in U.S. Pat. No. 7,025,429 (see FIG. 6). This practice, when extended to track rollers adjacent to the drive sprocket can lead to damage and avoidable wear of the drive sprocket. Further, under load conditions the rear drive sprocket pulls on the track to propel the crawler in a forward direction, drawing the track taut and, essentially, negating the need for the roller nearest the drive sprocket to be provided with costly suspension.

SUMMARY OF THE INVENTION

Disclosed herein is an undercarriage that may include a rigidly mounted roller near or adjacent to a rear drive sprocket. The remaining rollers and bogies may be flexibly suspended. Comparatively, the rigidly mounted roller may, among other things, serve to improve vehicular weight distribution across the track, reduce the number of parts in the undercarriage, increase protection from debris entering the tooth area of the drive sprocket and reduce ground or shock loads to the final drive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a vehicle that may make use of the invention;

FIG. 2 is a side view of a frame and a portion of an undercarriage making use of the invention;

FIG. 3 is a side view of a portion of the undercarriage that is not rotated with respect to the frame;

FIG. 4 is a side view of the portion of the undercarriage of FIG. 3 that is rotated with respect to the frame;

FIG. 5 is a side view of the undercarriage; and

FIG. 6 is a side view of a prior art undercarriage as disclosed in U.S. Pat. No. 7,025,429.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is an illustration of a work vehicle in which may the invention may be utilized. The dozer 10 illustrated, includes a cab 20, a body 30, a main frame 40, and a track frame assembly 100.

FIG. 2 illustrates a side view of a portion of the track frame assembly 100 as well as a portion of the main frame 40 and a rear sprocket drive 50 rigidly attached to the main frame 40 via a gearbox (not shown). As illustrated, the undercarriage 100 may include: a track frame assembly 200 having a first or stationary portion 200 a and a second or moving portion 200 b; an idler bogie arm 210 pivotally attached to the moving portion 200 b at pivot point 211; an idler 215, rotationally attached to a first end 210 a of the idler bogie arm 210 at 216; a first flexible pad 212 attached to a second end 210 b of the idler bogie arm 210; a first minor bogie arm 214, pivotally attached at the second end 210 b of the idler bogie arm 210 at pivot axis 213. Also illustrated is a first roller bogie arm 220 pivotally attached at a first end 220 a to the stationary portion 200 a at pivot shaft 221; a second flexible pad 222 attached to a second end 220 b of the first roller bogie arm 220; a second minor bogie arm 224, pivotally attached to the second end 220 b of the first roller bogie arm 220 at pivot axis 223. The illustration further includes a second roller bogie arm 230 pivotally attached, at a first end 230 a to the stationary portion 200 a at pivot shaft 231; a third flexible pad 232 attached to a second end 230 b of the second roller bogie arm 230; a third minor bogie arm 234, pivotally attached to the second roller bogie arm 230 at pivot shaft 233. Two rollers 217 may be rotationally attached to each of the minor bogie arms 214, 224 and 234 in a conventional manner and rotate about their respective axes 215′. The flexible connectors 212, 222 and 232 may be made of an elastomeric material and may be conventionally attached to the idler bogie arm 210 and the first and second roller bogie arms 220, 230 and the stationary portion as described. Stationary flexible pads 212′, 222′ and 232′ may be similarly attached to the stationary portion 200 a and positioned such that contact is maximized with their respective mating flexible pads 212, 222 and 232 as the second ends 210 b, 220 b and 230 b move closer to the stationary portion 200 a. Additionally, the flexible pads 212′, 222′ and 232′ may also be made of an elastomeric material. As illustrated, a fixed roller 300 is rotationally attached to the track frame 200 at fixed roller rotational axis 301 where the fixed roller rotational axis 301 is rigidly located with respect to the track frame 200. As shown in FIG. 5, the undercarriage 100 also includes a track 101. Note that only one track frame assembly 200 is illustrated in the Figures as the track frame 200 on the other side of the vehicle 10 may be an identical reflection of the illustrated track frame 200.

As illustrated in FIGS. 2, 3 and 4, the track frame 200 and the main frame 40 may be pivotally connected via a pivot shaft 201. As illustrated, a drive sprocket 50 may be rotationally connected to the main frame 40 via a final drive (not shown) and conventional housing structure (not specifically illustrated) and may rotate about an axis 51 having a fixed location with respect to the main frame 40. The track frame 200 may be slidably connected to a support bar (not illustrated). The support bar (not illustrated) may be pivotally connected to the main frame 40 midway between the track frames 200 and may limit the angular range of rotation for each track frame 200 about the pivot shaft 201 to a maximum angular range of, for example, ±3°.

As the vehicle moves along irregular areas of the ground, the roller bogie arms 220, 230 as well as the idler bogie arm 210 may pivot upon their respective axes 221, 231 and 211 in accordance with the demands of the terrain and the weight of the vehicle 10. Additionally, attached rollers 217 rotate about their respective axes 218 and the minor bogie arms 214, 224, 234 pivot about their respective axes 213, 223, 233 to accommodate irregularities as the weight of the vehicle 10 causes the track chain 110 to bend and conform to the contours of the ground.

As illustrated in FIG. 2, the fixed roller 300 may not flex, with respect to the track frame 200, to accommodate the contours of the ground as it may have an axis 301 that is rigidly fixed with respect to the track frame 200. Additionally, the fixed roller 300 may be placed as close as practicable to the drive sprocket 50. The proximity of the fixed roller 300 to the drive sprocket 50 may allow the fixed roller 300 to prevent a significant amount of debris from reaching the drive sprocket as the fixed roller will tend to crush and remove such debris prior to its contact with the drive sprocket 50. The fixed roller 300 may also reduce the amount of weight and shock loading borne by the drive sprocket 50 because it may be able to bear a substantial portion of any load in that location due to its proximity to the drive sprocket 50. As illustrated in FIG. 2, an axis of the pivot shaft 201 and the drive sprocket rotational axis 51 may be placed such that they are approximately equidistant from the ground, i.e., Y1≈Y2. Such an arrangement allows a minimal distance between the fixed roller 300 and the drive sprocket 50 and results in improved weight distribution as described above.

FIG. 4 illustrates the track frame at a maximum angular position of 3° with respect to the main frame, i.e., 3° in a direction that reduces the distance between an outer radius R1 of the fixed roller 300 and an outer radius R2 of the drive sprocket 50. (Note: FIGS. 2 and 3 show the track frame at an angular position of 0° with respect to the main frame. FIG. 2 illustrates R1 and R2.) In this exemplary embodiment of the invention a minimum distance X_(min), as shown in FIG. 4, between R1 and R2 at the maximum angular position illustrated for non-interference between the fixed roller 300 and the drive sprocket 50 may be in a range of 3 to 6 centimeters. Thus, the track frame 200, the main frame 40 and the drive sprocket 50 may be designed such that the distance between D1 and D2 is between 3 and 6 centimeters at the maximum angular position of 3°. Such a design may result in the minimum practicable distance between R1 and R2 at an angular position of 0°.

As described above and illustrated in FIG. 3, the fixed roller rotational axis 301 may move with respect to the drive sprocket rotational axis 51 whenever the track frame 200 rotates with respect to the main frame 40 about pivot shaft 201. As described earlier rotational movement between the track frame 200 and the main frame 40 for this exemplary embodiment may be restricted to a predetermined angular range of, for example, ±3°. Thus, in order to place the fixed roller 300 as close as practicable to the drive sprocket 50, the fixed roller 300 may be placed such that it avoids interference with the movement of the drive sprocket 50 when the relative angle between the main frame 40 and the track frame 110 is at its maximum (e.g., 3°) in a direction that reduces the distance between the fixed roller 300 and the drive sprocket 50. In this exemplary embodiment, the minimum practical distance D_(min) between the outer diameter D1 of the fixed roller 300 and the outer diameter D2 of the drive sprocket 50 may be between 3 and 6 centimeters when the relative angle between the main frame 40 and the track frame 200 is at its maximum of 3°.

Thus, assuming that the relative angle between the track frame 200 and the main frame 40 is approximately 0° at angle C of FIG. 4, the minimum practical distance D_(min) in FIG. 4 may equal (a2+b2−(2ab)×Cos (C−3°))^(1/2)−(D1+D2)/2. All undetermined angles and lengths may be determined using the law of sines and/or the law of cosines. Please note that the minimum practical distance for configurations other than this exemplary embodiment may be at any range greater that includes values greater than 0 centimeters at a maximum angle of any value greater or less than 0°.

Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims. 

1. An undercarriage comprising: a track frame; an idler bogie arm pivotally attached to the track frame; an idler rotationally attached to the idler bogie; a roller bogie arm pivotally attached to the track frame; a roller bogie pivotally attached to the bogie arm; a roller rotationally attached to the roller bogie a drive sprocket; and a fixed track roller adjacent to the drive sprocket and rotationally attached to an axle rigidly mounted to the track frame.
 2. The undercarriage of claim 1, further including a main frame having a main frame pivot shaft upon which the track frame pivots relative to the main frame, the mainframe pivot shaft having an axis.
 3. The undercarriage of claim 2 wherein the drive sprocket has a drive sprocket axis of rotation, the drive sprocket axis of rotation and the axis of the main frame pivot shaft at approximately equal vertical distance from a bottom of the track frame assembly.
 4. The undercarriage of claim 3 wherein a maximum angle by which the track frame pivots relative to the main frame is approximately 3°.
 5. The undercarriage of claim 3, further including an outer diameter for the fixed track roller and an outer diameter for the drive sprocket wherein the distance between the outer diameter for the fixed track roller and the outer diameter for the drive sprocket is within a range of 3 centimeters and 6 centimeters at a maximum relative angle between the track frame and the main frame.
 6. A work vehicle having an undercarriage comprising: a main frame having a rear pivot shaft; a track frame pivotally attached to the main frame at the rear pivot shaft, the track frame having a predetermined rotational limit; an idler bogie arm pivotally attached to the track frame; an idler rotationally attached to a first end of the idler bogie arm; a roller bogie arm pivotally attached to the track frame; a minor bogie pivotally attached to the roller bogie arm; a track roller rotationally attached to the minor bogie; a track; a rear drive sprocket having an axis of rotation and rotationally attached to the main frame; and a rear track roller rigidly mounted to the track frame and adjacent to the rear drive sprocket, the rear track roller having a rotational axis that is fixed with respect to the track frame, the rear track roller clearing the rear drive sprocket by a negligible distance when the track frame has been rotated to the predetermined rotational limit in a direction that reduces the distance between the rear track roller and the rear drive sprocket.
 7. The work vehicle of claim 3, wherein the axis of rotation and the rear pivot axis are at approximately equal vertical distances from the track chain on a side of the track assembly on which the both the rear track roller and the rear drive sprocket physically contact the track chain.
 8. The work vehicle of claim 3, wherein the negligible distance comprises a range of 3 to 6 millimeters.
 9. The work vehicle of claim 3, wherein the predetermined rotational limit is a range of ±3 degrees of angle or less. 